ESTRATIGRAFIA SÍSMICA DO PLATÔ DE PERNAMBUCO

RENATO OSCAR KOWSMANN, MÁRCIO PAULO DE ATAÍDE COSTA

Resumo


Two seismic reflection records across the Pernambuco Plateau, NE Brazil, obtained during the Woods Hole Cruise Chain 115 are examined in light of the onshore drilling and DSDP results in the Brazil Basin. The Pernambuco Plateau was formed due to the accumulation of sediments at least one second thick (two way travel time) behind seamounts outcropping from shallow basement believed to be 90 million years old. Sedimentation therefore began during the upper Cretaceous and was first interrupted probably during the Cretaceous-Tertiary boundary by a major erosional event. An intensification of oceanic circulation caused by a regression phase beginning in the latest Maestrichtian is called upon to explain the erosional unconformity detected in the profiles. Deposition resumed in the early Tertiary, and was again interrupted in the Oligocene. Widespread erosion carved deep incisions on the Plareau surface, exposing both early Tertiary and late Cretaceous sediments at that time. This event is correlated with the eustatic lowering of sea level and intensification of bottom currents associated with an increase in ocean basin capacity due to lowered sea floor spreading rates, and consequent decrease in mid-ocean ridge volume. Acoustically transparent late Tertiary and Quaternary sediments were deposited conformably over the Oligocene erosional topography.


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